With the acquisition, the athletic wear manufacturer also acquires new competitors like Nike, Jawbone, and Fitbit, all of whom have been aggressively exploring both wearable devices and tracking apps for those looking to get and stay in shape.

MapMyFitness is known for its app, rather than for any specific wearable device. The company, which will maintain its Texas-based operations post-acquisition, has always billed itself as an open platform dedicated to integrating with as many health and fitness tracking devices as possible. This strategy has helped the company amass 20 million registered users and integrate with more than 400 devices, including those created by Under Armour competitors like Nike and Adidas.

Early this year, Under Armour introduced Armour39, a wearable activity tracker for serious athletes that straps across the chest and monitors performance. It's as yet unclear what Under Armour's plans are for MapMyFitness, but CEO Kevin Plank says the company is now "better positioned to design open, digital products for the athlete of tomorrow and become more proactive in providing solutions that will help people across the world lead healthier lifestyles."